Much attention has been placed on optical recording media due to their high density and high capacity, and optical recording media are now used in a variety of applications. In particular, compared to standard removable magnetic recording media, optical recording media where data can be written once or rewritten by users (write-once optical recording media or rewritable optical recording media, hereinafter also generally referred to as “recordable optical recording media”) can record a large amount of data and can also record and reproduce the data in a short time. For this reason, such recordable optical recording media are coming into widespread use as removable storage media. As one example, a recordable optical recording medium includes a recording layer composed of various areas such as a basic information recording area (recording information areas such as a PCA (Power Calibration Area) and PMA (Program Memory Area)), a lead-in area, a data recording area (information area), and a lead-out area. With this type of recordable optical recording medium, the recording or reproduction (reading) of data is carried out by irradiating the recording layer with a laser beam set at the recording power or a laser beam set at the reproduction power (hereinafter, when no distinction is made, both are referred to as the “laser beam”). Here, when data is recorded on this recordable optical recording medium, the medium is irradiated with a laser beam set at the recording power in accordance with a data content of the data to form pits, where the light reflectivity differs for a laser beam set at the reproduction power used to irradiate the medium during reproduction, in the recording layer. By forming such pits, data is recorded in the recording area and data management information showing recording positions of such data, filenames, and the like is recorded in the lead-in area.
On the other hand, the present applicant has developed a multilayer optical recording medium 51 shown in FIG. 7 as a recordable optical recording medium that can record a larger amount of data than a normal conventional recordable optical recording medium. As one example, this multilayer optical recording medium 51 is a single-sided, two-layer optical recording medium that is rewritable, and is constructed of an L1 recording layer 3, a spacer layer 4, an L0 recording layer 5, and a cover layer 6 that are formed in layers in the stated order on a base 2 in the form of a flat plate (in a disc shape, for example) that has a fitting center hole H formed in a center part. This multilayer optical recording medium 51 is provided with two recording layers, the L1 recording layer 3 and the L0 recording layer 5, so that compared to a conventional recordable optical recording medium, double the amount of the data can be recorded. In this case, the base 2 is manufactured using a resin material and has a fine minute convexes and concaves (not shown) of grooves (guide grooves), lands, and the like formed in a surface (the upper surface in FIG. 7) on the cover layer 6 side. The L1 recording layer 3 is constructed of layers, such as a reflective film that reflects a laser beam, a phase change film whose optical coefficient is changed by irradiation with a laser beam set at the recording power, and a protective film that protects the phase change layer, formed on the fine minute convexes and concaves of the base 2. The spacer layer 4 is formed of light transmitting resin, and has a fine minute convexes and concaves (not shown) of grooves, lands, and the like formed in the surface on the cover layer 6 side. The L0 recording layer 5 is composed of layers, such as a phase change film and a protective film, formed on the minute convexes and concaves on the spacer layer 4. The cover layer 6 is formed of a thin film of a light transmitting resin so as to cover the L0 recording layer 5. By irradiating this multilayer optical recording medium 51 with a laser beam in the direction shown by the arrow A in FIG. 7, data is recorded on the L0 recording layer 5 and the L1 recording layer 3 and is read from the L0 recording layer 5 and the L1 recording layer 3.
In this case, the L1 recording layer 3 and the L0 recording layer 5 of the multilayer optical recording medium 51 have approximately the same area structure as the recording layer of a normal conventional recordable optical recording medium. More specifically, the L1 recording layer 3 is constructed of a basic information recording area 3b, a lead-in area 3a, a data recording area 3c, and a lead-out area 3d formed in order from the inner periphery side. In the same way as the L1 recording layer 3, the L0 recording layer 5 is constructed of a basic information recording area 5b, a lead-in area 5a, a data recording area 5c, and a lead-out area 5d formed in order from the inner periphery side. In this case, the basic information recording area 3b is composed of a PCA, a PMA, and the like for the L1 recording layer 3, and the basic information recording area 5b is composed of a PCA, a PMA, and the like for the L0 recording layer 5. Also, data management information Dt for the data Dd, Dd, . . . recorded in the data recording area 3c is recorded in the lead-in area 3a and data management information Dt (TOC) for the data Dd, Dd, . . . recorded in the data recording area 5c is recorded in the lead-in area 5a. 
When the data Dd, Dd, . . . are recorded on the multilayer optical recording medium 51, first the multilayer optical recording medium 51 is loaded into a recorder. In response to this, the recorder rotates the loaded multilayer optical recording medium 51 at a predetermined rotational velocity and moves a pickup above the lead-in areas 5a, 3a, and by emitting and focusing a laser beam in this state, sets the focal point of the laser beam on the lead-in area 5a, for example. Next, the recorder successively reads disc information Di recorded as wobble or pre-pits in the lead-in area 5a and the data management information Dt recorded as pits. At this time, based on the disc information Di, the recorder determines that this medium is a rewritable single-sided two-layer optical recording medium, and based on the data management information Dt the recorder specifies an empty area (an area in which data Dd has not been recorded) in the data recording area 5c and decides from which recording position the recording of data Dd is to start. Here, the data management information Dt is not recorded on a multilayer optical recording medium 51 that has not been used. Accordingly, when there is no data management information Dt in the lead-in area 5a, the recorder determines that the entire data recording area 5c is an empty area and decides to start recording the data Dd from the start position of the data recording area 5c. Also, on a multilayer optical recording medium 51 in whose data recording area 5c data Dd has already been recorded, data management information Dt showing the recording position of such data Dd is recorded in the lead-in area 5a. Accordingly, the recorder decides to start recording the data Dd from a start of an empty area specified based on the read data management information Dt. Next, the recorder moves the pickup to a position above the basic information recording area 5b and finds, according to a predetermined procedure, an appropriate laser power (recording power) for recording the data Dd onto the data recording area 5c. 
After this, the recorder moves the pickup to a position above the lead-in areas 5a, 3a, and by emitting and focusing a laser beam in this state, the laser beam is focused on the lead-in area 3a. Next, the recorder reads the data management information Dt recorded using pits in the lead-in area 3a. Here, in the same way as when the recording starting position for the data recording area 5c is decided, based on the existence of the data management information Dt or the data content of the read data management information Dt, the recorder specifies an empty area of the data recording area 3c and decides from which recording position the recording of the data Dd is to start. Next, the recorder moves the pickup above the basic information recording area 3b and finds, according to a predetermined procedure, an appropriate laser power (recording power) for recording the data Dd onto the data recording area 3c. Next, the recorder moves the pickup above the data recording areas 5c, 3c, focuses on the data recording area 5c, for example, and then starts to record the data Dd, Dd, . . . from a start position of the data recording area 5c. In this case, when the data Dd has been recorded up to a final position of the data recording area 5c, the recorder focuses on the data recording area 3c and then continues the recording of the data Dd, Dd, . . . from the start position of the data recording area 3c. When the recording of all of the data Dd, Dd, . . . has been completed, the recorder moves the pickup above the lead-in areas 5a, 3a and focuses on the lead-in area 5a. Next, the recorder records data management information Dt on the data Dd, Dd, . . . recorded in the data recording area 5c in the lead-in area 5a. In the same way, the recorder then focuses on the lead-in area 3a and then records data management information Dt on the data Dd, Dd, . . . recorded in the data recording area 3c in the lead-in area 3a. By doing so, the recording of the data Dd, Dd, . . . on the multilayer optical recording medium 51 is completed.